Abstract

This paper describes the performance of a solar water heater with an alternative
working fluid. A solar flat plate collector of fIxed orientation was fabricated and
connected to a heat exchanger, which was kept inside the water storage drum.
The developed collector was a low temperature device operating with the
temperature range of ambient to 100°C. Acetone was selected as an alternative
working fluid and allowed to re-eirculate in a closed loop. A shell and tube type
heat exchanger (non-mixing) was designed and fabricated for the heat transfer between acetone and water. The solar intensity increased from 55 mw/cm2 at
8.30 am to 85 mw/cm2 at 1.30 pm and decreased to 64 mw/cm2 at 5.00 pm.
The absorber plate temperature, which remained nearly constant for the first
two hours, went up to 90°C in the next two hours. It was nearly constant from
11.00 am to 1.30 pm and then dropped down to 72°C in the afternoon. The
hot fluid was found to loose heat to the surrounding water at more or less
constant rate from 11.30 am to 5.00 pm. The highest temperature of acetone
(70°C) was observed during 1.00 pm to 2.00 pm. The temperature of water
increased from 30°C to a maximum of 62°C. Overall efficiency of the system was
found to be 45% while considering the solar input to the heat gained by the
water. Alternative working fluids such as acetone, methanol or ethanol may be
considered for substituting water in the flat plate collector in view of the fact
that the fluids have low boiling point coupled with high latent heat of
evaporation.